Device for measuring the thickness of walls or the like, subject to erosion



May 17, 1949. H. Y. LANKFORD 2,470,493

DEVICE FOR MEASURING THE THICKNESS OF WALLS OR THE LIKE SUBJECT To EROSION Filed Oct. 21, 1946 Jig.

3/ g :1 I 4 125., 25 g '6 '2; 2% x, 11 J INVENTOR.

' Howard K Law/(ford 28 BY ll/J ATTWf/YEY Patented May 17, 1949 DEVICE FOR MEASURING THE THICKNESS F WALLS OR THE LIKE, SUBJECT TO EROSION Howard Y. Lankford, Gary, Ind., assignor to Carnegie-Illinois Steel Corporation, a corporation of New Jersey Application October 21, 1946, Serial No. 704,645

Claims. (01. 33-143) This invention relates to provisions for gauging the deterioration by erosion of furnace roofs and more particularly the roofs of metallurgical open hearth furnaces, although not limited thereto.

In the manufacture of steel by the open hearth method, the furnace charge must be reduced to a bath of molten steel which must be maintained for a substantial period of time. During the operation of the furnace it is desirable to approach as nearly as possible an even temperature throughout the bath. To accomplish this an even temperature must be kept in the furnace above the bath, as all the heat for melting the charge is applied between the roof of the furnace and the bath. Uneven distribution of the heat may cause a more heterogeneous steel, and also may cause hot spots inthe furnace roof resulting in weakening of the refractory brickwork of which it is composed.

As the construction of the roof of an open hearth furnace is that of an arch, varying, and often great, compression stresses are introduced by fluctuations in temperature. Of course, weak spots in the brickwork generally account for the fact that the roof has become thinner in certain places, and they cannot be entirely prevented.

' If the tendency of the roof to become thin in spots is discovered in time it is possible to arrest the erosive action by changing the direction of the flame slightly away from the weak spot and thereby prolong the life of the roof. In addition, accurate determination of the thickness of the roof at certain intervals would enable the masonry department to be accurately guided in scheduling roof repairs.

Up until the present time the need for partial or complete rebuilding of the roof of an open hearth furnace has mainly been determined by the number of heats to which the roof has been exposed and the expectant life of the particular refractory brick of which it is composed.

Investigation of a large number of present day open hearth furnaces indicates that the average roof must be completely rebuilt after approximately 200 heats. While hot spots in the furnace roof generally indicate a thin roof, it has frequently been discovered, after the brickwork has been torn down, that the roof actually was in better condition than anticipated and would have rendered good service for an additional number of heats. On the other hand, the brickwork of the roof is sometimes weaker than would appear, even though no hot spots occur, .with

. 2 the end result that the roof caves into the hearth of the furnace.

Even if the actual physical condition of the furnace roof could be determined by visual inspection through the charging door of th furnace, certain disadvantages result, among them being that the admission of an excess of air through the open furnace door causes poor fuel economy and cooling of the furnace.

In view of the foregoing, it will be readily appreciated that numerous advantages would accrue from an accurate determination of the actual physical condition of the roof of a metallurgical open hearth furnace, but so far as I am aware the prior art has failed to provide a means for accomplishing this end.

Now, it is among the objects of the present invention to provide certain accessories which will be operable to effect an accurate determination of the thickness of the bricks of which a furnace roof is composed at various critical locations with the attendant advantages enumerated hereinbefore. That is to say, the necessity for making roof repairs may be accurately determined.

A further object is the attainment of the foregoing by means which are inexpensive to manufacture, install, operate, and maintain.

The invention, then, comprises the features hereinafter described and as particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative of several of the number of ways in which the principles of the invention may be employed.

In said drawings:

Figure 1 is an elevational view, partly in section, of a measuring device embodying the present invention; and

Figures 2 and 3 are fragmentary elevational views, partly in section, illustrating, respectively, the upper and lower ends of the measuring device, when the said device is ready for insertion into and through the roof of a furnace in a manner to be more fully described hereinafter.

Referring more particularly to the drawings, the roof of a typical metallurgical open hearth furnace is shown at 2. The roof 2 is of familiar arch design and composed for the most part of the usual refractory brickwork which as such forms no part of the present invention. At certain spaced positions the roof 2 of the furnace is provided with a sectional refractory brick which extends the full thickness of the roof.

acvones 3 Each of these sectional bricks is composed of a pair of vertically opposed refractory brick elements 3 which, when assembled, provide a composite rectangularly shaped brick with a longitudinally (and vertically) extending frusto-conical bore 4. Within the frusto-conical bore 4 provided by each assembled pair of brick elements 3 there is fitted a conformingly shaped tubular refractory liner 6', the latter also having a frustoconical bore. The shape of the liner is preferably achieved by the use of walls of substantially mounted for pivotal movement, the construction and arrangement being such that the lever 24 may move from a position entirely within pipe IE to a position wherein it will project from both sides thereof through slots 24 and 33.

As shown most clearly at the bottom of Figure 1, one end of the detent 24 is shaped to provide a cam surface 28, adapted to project through the short longitudinal slot 30 in the pipe IS. The

uniform thickness, whereby the largest diametral portions of both the exterior and interior thereof are at the same end of the liner, and its length is substantially the same as the corresponding dimension of the sectional refractory brick within which it is disposed.

During the operationof the furnace a plug (not shown), shaped nicely to the contour of the frusto-conica'l bore of the tubular refractory liner 5, is ordinarily seated within the bore of its cooperating liner, the latter, as hereinbefore stated, being seated within the bore 4 provided between a pair of the oppositely assembled brick elements 3. Upon the removal of one of the plugs it may be determined from the inner end thereof whether erosion has taken place, and in order for this determination to have practical significance the height of the liners 6, brick elements 3 and the shanks of the plugs are coterminous with the thickness of the brick of which the furnace roof is composed.- Therefore, upon the removal of one of the plugs, and the observation of the condition at the inner end thereof, the progress of erosion of the inner surfaces of the brickwork of the roof at that particular point may be accurately determined, preferably in a manner which will be described hereinafter.

In addition, various measuring accessories or instrumentalities may be inserted through the aperture in the roof thus provided for the purpose of making determinations regarding temper ature, direction of flame-flow, and so forth.

In an open hearth furnace of conventional shape and size three test openings arranged crosswise of the furnace roof at five spaced points in the length thereof should ordinarily be sufficient to enable accurate determination of the condition of the furnace roof at any given point. More specifically, one row may be situated over each knuckle, one row at the tapping hole of the furnace, and one row half-way between the tapping hole and the knuckles. It is to be understood, however, that the number and location of the test holes can best be determined empirically. The test holes may be made accessible from the top of the furnace by providing walks above the furnace buckstays.

In Figures 1 through 3, there is illustrated a measuring device which may be satisfactorily utilized to make the determinations contemplated by the teachings of the invention. More specifically, this measuring device comprises two lengths of pipe l5 and I6 which are joined together by a pipe coupling IT to form a sectional tube. Disposed within this sectional tube is a slide rod I8 which projects from the outer end of one of the pipes (the pipe [6 in Figure 1) and terminates in a handle 20. Between the handle 20 and the outer end of the pipe IS the rod l9 carries a collar 2| which limits the inward movement thereof.

The lower end of the rod I!) always remains within the pipe IS. The rod is slotted as shown at 23, to accommodate a detent 24 which is ends of slot 34 are bevelled as shown at 3| to aid cooperation of the cam surface 28 of the lever 24 in its inward and outward movement with respect to the said short slot. Immediately opposite the short slot 30 the lower pipe I5 is provided with a longer slot 33, the upper end of which is squared as shown at 34, while the lower end is bevelled in the manner shown at 36.

Referring still to Figure 1, each of the pipe lengths I5 and I6 is provided with a slidable collar 40 to which there is secured a gauge rod 42 which extends longitudinally of the said pipes. One end of the rod 42 projects from the collar 40 on the pipe 15 and terminates in a foot 44, while the other end of the rod 42 projects from the collar 40 on the pipe l8 and terminates in an outwardly extending handle 45. Adjacent the handle 45 the rod 42 is provided with a lug 41 which cooperates with a spring 49 to hold the rod in the position shown in Figure 1. Preferably too, the Pipe "5 is provided with calibrations (not shown) in conjunction with which the lug 41 may serve as a pointer for determining the relative position of the rod 42 with respect to the rod IS.

The foregoing construction and arrangement may be utilized, in the following manner, to accurately determine the thickness of the brickwork of the roof 2 of the furnace at any point wherein the said roof is provided with the assembly of refractory elements hereinbefore described (i. e. the brick elements 3, liners 6 and the plugs).

' The handle 20 on the upper end of the rod I9 is pushed downwardly until the detent 24 is completely confined within the lower end of pipe [5. The operator then inserts the measuring device by holding the pipe E5 in one hand and the handle 20 in the other, keeping the latter in its lowered position. After the end of the pipe it has been inserted into the furnace a sufficient distance to expose the slots 30 and 33 on the interior thereof, the operator raises the handle 20, thus forcing the detent 24 into the position shown at the bottom of Figure 1, by engagement of its cam surface 28 with the upper end of slot 30. The operator then removes his hand from the pipe [6 and pulls upwardly on the handle 20 until the ends of the detent engage the underside or inner ends of the brick elements 3. At the same time, the operator releases the spring 49 from engagement with the lug 41 to permit the measuring rod 42 to drop until the foot 44 on the lower end thereof engages the upper ends of the brick members 2 and their liner 6. From the position of the measuring rod 42 with respect to the graduations on the pipe I 6 the extent of erosion of the inner surface of the furnace may be accurately determined.

Preferably, the lower end of the pipe Iii; reamed to form a cutting edge which will assist in removing any obstructions which may accumulate in the opening of the liner 6. By utilizing the sectional construction (1. e. the pipes 15 and 16 connected by the pipe coupling 11), the lower section may be easily replaced when burned out.

The collar 2| on the rod is limits the movement of the pivoted detent 24 downwardly oi the pipe Ii. The cam end 20 of the detent is shaped so that it tends to enter slot 30 when the rod is is raised from its lowermost position in pipe l5.

While I have shown and described certain speciflc embodiments of the present invention, it will be readily understood by those skilled in the art that I do not wish to be limited exactly thereto. since various modifications may be made without departing from the scope of the invention as delined in the appended claims.

I claim:

1. A thickness-measuring device for walls or the like comprising a tube having one end adapted to be inserted through an opening in a wall, a slide rod extending into the other end of said tube, a detent pivoted on said rod within said tube, said tube having a slot adjacent said one end permitting tilting of the detent to a position transverse to the rod in which it is engageable with the inner edge of said opening and a gauge rod slidable on said tube having a portion adapted to engage the exterior of the wall.

2. A device as defined by claim 1 characterized by said detent having a cam surface at one end tending to enter said slot on axial movement of the slide rod in one direction in the tube.

3. A device as defined by claim 1 characterized by a scale on said tube cooperating with an index on said gauge rod.

4. A device as defined by claim 1 characterized by said one end of the tube having a cutting edge thereon.

5. A device as defined by claim 1 characterized by stop means on said slide rod engageable with said tube limiting movement of the former through the latter.

HOWARD Y. LANKFORD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 54,229 Tait Apr. 24, 1866 105,210 Horton July 12, 1870 734,014 Traut July 21, 1903 745,357 Lanham Dec. 1, 1903 773,149 Junge Oct. 25, 1904 853,841 Teeple May 14, 1907 1,856,295 Sovatkin May 3, 1932 FOREIGN PATENTS Niunber Country Date 116,377 Switzerland Jan. 3, 1927 170,917 Germany May 28, 1906 

